cve/2017/CVE-2017-3737.md

### [CVE-2017-3737](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-3737)
![](https://img.shields.io/static/v1?label=Product&message=OpenSSL&color=blue)
![](https://img.shields.io/static/v1?label=Version&message=n%2Fa&color=blue)
![](https://img.shields.io/static/v1?label=Vulnerability&message=Unauthenticated%20read%2Funencrypted%20write&color=brighgreen)

### Description

OpenSSL 1.0.2 (starting from version 1.0.2b) introduced an "error state" mechanism. The intent was that if a fatal error occurred during a handshake then OpenSSL would move into the error state and would immediately fail if you attempted to continue the handshake. This works as designed for the explicit handshake functions (SSL_do_handshake(), SSL_accept() and SSL_connect()), however due to a bug it does not work correctly if SSL_read() or SSL_write() is called directly. In that scenario, if the handshake fails then a fatal error will be returned in the initial function call. If SSL_read()/SSL_write() is subsequently called by the application for the same SSL object then it will succeed and the data is passed without being decrypted/encrypted directly from the SSL/TLS record layer. In order to exploit this issue an application bug would have to be present that resulted in a call to SSL_read()/SSL_write() being issued after having already received a fatal error. OpenSSL version 1.0.2b-1.0.2m are affected. Fixed in OpenSSL 1.0.2n. OpenSSL 1.1.0 is not affected.

### POC

#### Reference
- http://www.oracle.com/technetwork/security-advisory/cpujan2018-3236628.html
- http://www.oracle.com/technetwork/security-advisory/cpujul2018-4258247.html

#### Github
- https://github.com/ARPSyndicate/cvemon
- https://github.com/chnzzh/OpenSSL-CVE-lib
- https://github.com/javirodriguezzz/Shodan-Browser
- https://github.com/tlsresearch/TSI